The IEEE 802.11 standard describes a Time Synchronization Function (TSF), which allows stations to update their clocks. The stations only update clocks forward, not backward.
U.S. Pat. No. 6,718,395 to Ziegler describes a method and apparatus for synchronizing with communication traffic in a Bluetooth network without joining the network. The apparatus transmits an inquiry signal and receives an inquiry response signal having a coarse system clock time. The apparatus uses the coarse system clock time for estimating an initial channel in a channel hopping sequence then advances channels through the sequence in steps of four or more for scan window time periods of four or more time slot periods until a communication traffic signal is recognized. The time-of-arrival of the traffic signal is used for refining the coarse system clock time in order to acquire the exact system clock time. The exact system clock time is used by the analyzer for deriving the channels and timing of the sequence for synchronizing to subsequent communication traffic signals.
KR patent 4,056,474 to Electronics and Telecommunications Research Institute describes a method for synchronizing two or more devices by setting a common clock using a UTC (Universal Time Clock). The UTC is obtained through another device such as a GPS (Global Position System).
U.S. Pat. No. 7,151,945 to Myles et al. describes a method and apparatus for synchronizing a local clock value in a wireless receiver receiving a data unit containing synchronization information. The method includes receiving a first data unit containing synchronization information, extracting the synchronization information from the received first data unit, copying a local free-running clock at a known reference point in time relative to the time the first data unit was received to generate a local timestamp; and calculating an offset to the free-running clock using the extracted synchronization information and the local timestamp, the calculating in non real-time, such that the sum of the calculated offset and the value of the free-running clock provides a local clock value that is approximately synchronized in time. The apparatus implementing the method is part of a node of a wireless station, and provides a time synchronization function, typically at the MAC layer.
Additional background art includes:                U.S. Pat. No. 7,180,915 to Beyer et al.;        Published US Patent Application 2004/0223484 of Xia et al; and        Published PCT Patent Application WO 2005/029777 of Koninklikje Philips Electronics, N.V.        
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.